In a fuel cell system equipped with a water reservoir arranged to accumulate water discharged from fuel cells, one proposed structure provides a temperature sensor in the water reservoir to identify the status of the water reservoir.
Size reduction or weight reduction of the fuel cell system has been highly demanded to allow the fuel cell system to be compactly mounted on a vehicle or another equivalent moving body. It is accordingly required to develop a technique of identifying the status of the water reservoir without using the temperature sensor in the fuel cell system.